Abstract:

Objective  To perform quantitative comparison of microanatomical features between subtemporal and presigmoidal minimally invasive approaches for exposing petrous apex on the basis of virtual reality image model.  Methods  CT and MRI were performed on 15 adult cadaver heads (30 sides) to establish virtual reality three-dimensional anatomical model of petrous apex. The superior edge of the root of temporal bone zygomatic process and the mastoidale on the calvaria were selected as landmark points of craniotomy through subtempral and presigmoidal approaches. Petrous apex was selected as exposure landmark point on the skull base. The lines between craniotomy and exposure landmark points were used as axis to outline a cylinder simulating surgical routes of subtemporal and presigmoidal approaches. Anatomical exposures in two surgical routes were observed and measured. Statistical comparison was launched by paired t test.  Results  Surgical route of subtemporal approach passed through middle skull base and temporal lobe, and then reached petrous apex. Petrous bone drilling was performed to expose internal acoustic meatus, facial nerve and labyrinth. Then, trigeminal nerve, superior petrous sinus and cavernous sinus were exposed. Surgical route of presigmoidal approach was performed by drilling petrous bone through mastoid and passing vertical segment of facial nerve. Then, glomus jugulare, the lower cranial nerves, ossicular chain, labyrinth and internal carotid artery (ICA) were exposed in turn. Reaching internal acoustic meatus, the route exposed anterior inferior cerebellar artery (AICA) and facial-acoustic nerve complex. Reaching petrous apex, the route involved superior cerebellar artery, superior petrous sinus, inferior petrous sinus, cavernous sinus, trigeminal nerve and partial temporal lobe. The volumes of route, osseous structures, facial-acoustic complex, labyrinth and vein involved in presigmoidal approach were more than those in subtemporal approach (P = 0.000, for all). Volumes of temporal lobe, trigeminal nerve and ossicular chain involved in subtemporal approach were more than those in presigmoidal approach (P = 0.000, for all). Volume of lower cranial nerve and artery involved in presigmoidal approach was (32.38 ± 2.86) mm³ and (262.74 ± 16.93) mm³ respectively, but above structures were not involved in subtemporal approach.  Conclusions  Exposure of structures in and around petrous bone in presigmoidal approach is more than that in subtemporal approach. Thus, more attention should be paid to protect critical structures in presigmoidal approach. Subtemporal approach can reach petrous apex through temporal lobe, thus it is suitable to treat lesions in middle skull base which implicate petrous bone and push temporal lobe upward.

Key words: Petrous bone, Neuroanatomy, Microsurgery

摘要：

目的 在虚拟现实解剖模型中量化比较经颞下入路与经乙状窦前入路显露岩尖部的显微解剖学特征。方法 利用15 例（30 侧）尸头CT 和MRI影像构建岩尖部虚拟现实三维解剖模型。在颅盖上分别选取颞骨颧突根部上缘和乳突尖部为经颞下和乙状窦前入路的开颅标记点，颅底上选择岩尖部为显露标记点，以开颅和显露标记点连线为轴线作圆柱模拟经颞下和乙状窦前入路手术路径，观察和测量两种手术路径中解剖结构显露情况，采用配对t 检验进行比较分析。结果 经颞下入路手术路径经过颅中窝底和颞叶到达岩尖部，磨开岩骨后显露内耳道、面神经和迷路，向前显露三叉神经、岩上窦和海绵窦。经乙状窦前入路经乳突磨除岩骨，经面神经垂直段向深部依次显露颈静脉球、后组脑神经、听骨链、迷路和颈内动脉，路径到达内耳道时显露小脑前下动脉和面听神经复合体，到达岩尖部时包含小脑上动脉、岩上窦、岩下窦、海绵窦、三叉神经和部分颞叶。经乙状窦前入路手术路径中骨性结构、面听神经复合体、迷路和静脉体积均大于经颞下入路（P = 0.000），颞叶、三叉神经和听骨链体积均小于经颞下入路（P = 0.000）。经乙状窦前入路中包含后组脑神经体积为（32.38 ± 2.86）mm³、包含颅底动脉体积为（262.74 ± 16.93）mm³，经颞下入路不包含上述结构。结论 经乙状窦前入路对岩骨周围和岩骨内结构的显露范围多于经颞下入路，对重要结构保护较好；经颞下入路经过颞叶到达岩尖部，适用于治疗累及岩骨并将颞叶向上推挤的颅中窝病变。

关键词: 颞骨岩部, 神经解剖学, 显微外科手术